Never forget reversion to the mean.Strong performance by a mutual fund is highly likely to revert to the stock market norm—and often below it.

Stay the course. Regardless of what happens in the markets, stick to your investment program. Changing your strategy at the wrong time can be the single most devastating mistake you can make as an investor.

‘Markets Have Been Solidly Upward’

“Over the long run, the growth trends in our economy and financial markets have been solidly upward, despite the gyrations and uncertainty we inevitably experience as the years roll by,” Bogle concluded.

“It is reasonable to assume that this growth will continue,” he said. “Do not let false hope, fear and greed crowd out good investment judgment. If you focus on the long term and stick with your plan, success should be yours.”

Bogle founded Vanguard, the largest mutual fund manager and the second-largest ETF issuer in the U.S., with more than $720 billion in ETF assets alone. Vanguard is known for its low-cost focus, and among its 70 ETFs in the market are giants such as the $79 billion Vanguard Total Stock Market ETF (VTI) and the $68.7 billion Vanguard S&P 500 ETF (VOO), both of which cost only 0.04% in expense ratio, or $4 per $10,000 invested.